First, let me say thanks to all. I've learned a great deal from this forum.
My sump pump (1/3 HP Little Giant) works well only when the float switch is in control. I tried an electronic switch to increase my cycle time, but after one good cycle and the pit has filled, the pump turns on without pushing any water. My first thought was air lock, but there is a vent hole and water is streaming out of it when the pump is running. With the mechanical float switch, everything works fine unless I manually empty the water level to below where the float turns the pump off. In this case I get the same results on the next cycle as with the electronic switch Ė the motor turns on at the right time but no water moving (except out of the vent hole).
The only difference between the two is the difference in the water level that the pump is turned off. I have about 13 feet of head to overcome, plus a check valve, and I wonder if the pump isnít getting enough pressure right away to open the check valve. I tried putting a pipe clamp over the vent hole to block most of the flow but it did not help.
My thoughts are that I could increase the distance between the check valve and pump (currently about 6Ē), replace the pump with a more powerful one (though the little battery powered pump works fine) or add another check valve higher in the line. Any thoughts?